1. Technical Field
The present invention relates to a fabricating method of a lithium electrode, a lithium electrode, and a lithium secondary battery including the same.
2. Description of the Related Art
A lithium battery may be classified into a lithium primary battery and a lithium secondary battery depending on whether or not the battery is rechargeable. The lithium primary battery uses lithium for an anode, and is classified depending on kinds of a cathode. However, the lithium primary battery has a disadvantage in that a utilization rate of an electrode is deteriorated due to non-uniformity of potential distribution caused by a localized dissolution reaction of a lithium electrode.
Meanwhile, the lithium secondary battery has a structure in which a non-aqueous electrolyte including a lithium salt is impregnated in an electrode assembly including a cathode, an anode, and a porous separator interposed therebetween, wherein the cathode and the anode are applied with a cathode active material and an anode active material, respectively, on a current collector. Examples of the cathode active material applied to the cathode mainly include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium composite oxide, and the like, and examples of the anode active material applied to the anode include a carbon-based material, and the like. The lithium secondary battery has been actively researched in order to increase energy density of the battery.
In order for the lithium secondary battery to exhibit high energy density, a method of coating a slurry on an aluminum as the cathode and a copper foil as the anode, the slurry including increased weight of active materials per unit gram, drying the coated slurry, and a press process such as a roll press process, or the like, to increase electronic conductivity among the active materials, thereby improving long lifespan and high-rate charge and discharge characteristics, has been commonly performed.
However, when the electrodes are pressed by a roll press, or the like, the active materials are broken by the roll and the electrode in contact to each other, and accordingly, pressure is delivered to an inner side, whereby particles of the active materials are continuously destroyed toward the foil. FIG. 1 is scanning electron microscope (SEM) images each illustrating the particle breakage. Description regarding this is provided again in the detailed description of the present invention below.
Eventually, deterioration of the electrode occurs from the outermost layer of the electrode layer, which reduces electronic conductivity among the active material particles, and causes increase in resistance of the cathode and the anode, and lithium deposition due to side reactions, such that desirable long lifespan and high-rate charge and discharge characteristics may not be obtained.
Nevertheless, the roll press process of the electrode is an essential process, which is inevitably applied in order to maintain the electronic conductivity among the entire inner active materials, even if damage to some of active material particles from a surface may occur. Therefore, necessity of a technology of preventing damage to the active material particles after the roll press process has been increased.